The goals of this proposal are to define (a) the mechanisms by which the peptide mediator bradykinin interacts with its receptors, and (b) the response of specific receptor-bearing target cells: the fibroblasts found in interstitial connective tissue. Initial studies will be carried out in specific cultured cell systems which express bradykinin receptors, including the human lung fibroblast strains W1-38 and IMR-90, additional strains of both human lung and skin fibroblasts which we will develop, and the HSDM1C1 murine fibrosarcoma established cell line. Receptor number and affinity will be determined by radioligand binding, and structure/activity relationships for natural bradykinin-related peptides, synthetic analogs, and receptor antagonists will be assessed. Receptor desensitization will be explored for relative contributions of cyclic nucleotides, functional or physical uncoupling of receptor from linked pathways, and target cell degradation of bound ligand, possibly by a receptor-associated mechanism. The target cell responses to be defined include amount and type of arachidonate derivatives produced via the cyclo-oxygenase and lipoxygenase pathways, changes in cyclic nucleotide levels and alterations in total cell protein synthesis. This project will assess whether a particular bradykinin receptor may correlate with a specific target cell response, such as increased protein synthesis or production of characteristic secondary mediators related to inflammation or trauma. These studies will then be extended to freshly-isolated human lung fibroblasts and intact lung tissue slices. The proposed research will define the mechanisms of bradykinin receptor-mediated biologic activities. It will seek to determine if these are similar in skin and lung fibroblasts, or if they differ in lung fibroblasts in some way which contributes to the development and progression of human lung injury.